Extention of the perceived color gamut and improved color nuances for displays using a simple software-based solution

A special software makes specific, imperceptible modifications to images of a sequence whereby the viewer gets the impression of a greater color gamut (amount of displayable colors) compared to a display without this innovative software-support ("conventional display"). Color nuances in image areas with saturated colors are improved. The invention is suitable, among others, for all monitors, TVs or VR-displays.

The so-called color gamut, the set of displayable colors in a display, is limited by the primary colors used. Only such colors can be produced by the display that are created by additive mixing of these primary colors. However, humans can perceive a larger set of colors beyond the color gamut. Additionally, in reality as well as in photo­graphic/image material, often color stimuli occur, which cannot be reproduced exactly by any conventional display.

Image sequences and video material often comprise saturated colors that can be perceived by the human visual system but not be produced by displays. For display on screens, these colors are usually mapped to less saturated colors by means of so-called gamut mapping (color space transformation and clipping). However, this procedure leads to a loss of detail, in particular in vivid color areas of the image. This problem can be reduced by choosing other, more elaborate primary colors, but never completely avoided. That is a fundamental technical limitation to all current display technology.

The human visual system continuously adapts to stimuli from the environment, e.g. to ambient light or to viewed images. With the so-called chromatic adaptation, the perception of colors alters: a stimulus (e.g. the emission spectrum of a display pixel) produces different color impressions depending on the viewer's adaptation. For example, if an observer becomes adapted to a particular hue, complementary hues perceived shortly thereafter will result in colors perceived more saturated than without this prior adaptation.

By specifically changing the images displayed in a sequence, the chromatic adaptation can be controlled – with only minimal and imperceptible color deviation – so that in subsequent frames color impressions are created for the viewer that lie outside the color gamut of a conventional display. In this way, more saturated color impressions can be generated.

The algorithm underlying this inventive method analyzes image sequences (e.g. videos or images from interactive applications) and modifies the individual images with regard to the presented colors in such a way, that a specific chromatic adaptation takes place. By this, the properties of the human vision can be exploited to create perceived colors, which a conventional display is not able to produce without this invention. This purely software-based solution can be used with image sequences on all kinds of displays, such as monitors, TVs, projectors and VR-displays at run-time, or during the creation of the image material to compensate for the technical limitations mentioned above.

• purely software-based method for enhanced visual perception of colors in image sequences (no hardware modifications necessary)
• color impressions outside the conventional color gamut can be created specifically
• rendition of saturated colors improved on all types of display
• broad area of application: monitors, TVs, projectors, VR-displays etc.

The invention is in the area of rendition of image sequences on various display devices.